<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
    }
    
    body {
        padding: 100px;
    }
    
    textarea {
        width: 200px;
        height: 100px;
        border: 1px solid pink;
        outline: none;
        resize: none;
    }
    
    ul {
        margin-top: 50px;
    }
    
    li {
        list-style: none;
        width: 300px;
        padding: 5px;
        background-color: rgb(245, 209, 243);
        color: red;
        font-size: 14px;
        margin: 15px 0;
    }
</style>

<body>
    <textarea name="" id=""></textarea>
    <button>发布</button>
    <ul>

    </ul>
    <script>
        var btn = document.querySelector('button');
        var text = document.querySelector('textarea');
        var ul = document.querySelector('ul');
        btn.onclick = function() {
            if (text.value == '') {
                alert('您为输入内容，请输入内容！');
                return false;
            } else {
                var li = document.createElement('li');
                li.innerHTML = text.value;
                ul.insertBefore(li, ul.children[0]);
            }
        }
    </script>
</body>

</html>